When Emmanuel Macron rose to power, he put the environment at the heart of his agenda. Eighteen months later, anger over those policies has stoked protests that are a huge challenge for the French president.

Rioters torched cars and buildings in central Paris on Saturday following two weeks of protests caused partly by higher fuel taxes which Macron says are needed to fight climate change. Some protesters called for him to resign.

Macron’s plight illustrates a conundrum: How do political leaders’ introduce policies that will do long-term good for the environment without inflicting extra costs on voters that may damage their chances of re-election?

It is a question facing leaders across the world as delegates hold talks in the Polish city of Katowice this week to try to produce a “rule book” to flesh out details of the 2015 Paris Agreement on fighting climate change.

“Clearly, countries where inequalities are the highest are the ones where these kinds of push-backs are mostly likely,” Francois Gemenne, a specialist in environmental geopolitics at SciencesPo university in Paris, said of the political risks.

Naming Italy, the United States and Britain as countries where environmental moves could risk a voter backlash, he said: “I guess it’s one of the reasons why populist leaders tend to be very skeptical about climate change and environmental measures.”

The protests in France have inspired a similar movement in neighboring Belgium, where protesters took to the streets on Friday.

There have also been small-scale protests in Canada over Prime Minister Justin Trudeau’s plan to impose a federal carbon tax on provinces unwilling to combat climate change.

What was once widely seen by governments as a win-win transition to cleaner energies now looks more like causing short-term costs with huge social disruption, followed by possible long-run gains.

Another challenge facing leaders is over how they use the proceeds from policies intended to help the environment: Should money raised from carbon taxes be used directly to combat climate change, or to plug holes in national accounts?